Non-Invasive Prenatal Testing (NIPT) Faetsheet

Non-Invasive Prenatal Testing (NIPT) Faetsheet
Current Screening Technologies: Matemal Serum Screening
Current screening technologies generally involve measuring biochemi.
cal markers associated with trisomy 21, as well as trisomy 18 and 13, in
maternal serum during the first and/or secane trimester. An ultrasound
measuring letal nuchal translucency (NT) is often included in a first trio
mester screen as an additional marker 01 trisomy 21. After firsl or second
trimester screening, the woman typically receves a revised risk for triso-
my 21 that is calculated based on her maternal age risk, the results of
the serum screen, and the NT measurement .:.1available)
An advantage 01 screening is that it is non-invasive, thus posing no risk
to the felus. Only women whose revised risk exceeds a laboratory and
test-dependent cut-off are candidates tor diagnostic testing by chorionic
villus sampling or amniocentesis, An inherent limitation of this approach
is that screening only detects 85-95% olletuses with triscmy 21, and
falsely designates 3-6% of pregnancies as .positive~ when they are, in
fact, unaffected with trisomy 21. For every trisomy 21 fetus detected, per-
haps 25 Mil be subjected to the risk of an inv3sive procedure.
Current Testing Technologies: Chorionic Villus Sampling (CVS)
or Amniocentesis
An alternative to screening is invasive prenatal diagnosis by chorion-
ic villus sampling (CVS) or amniocentesis which directly assesses the
chromosome constitLtion of the fetus through cells from the pregnancy.
The advantage is the diagnostic certainty at cetecting trisomy 21, 18, and
13. In addition, testing fetal cells and the amniotic fluid may allow for the
detection of other chromosome abnormities, genetic conditions, or open
neural tube defects. The downside is that these procedures are associ-
ated with a measurable risk of a procedure-related miscarriage or other
adverse pregnancy outcome.
Publication Acknowledgements
Developed under an educational grant from Sequenom. Copyright 2012
by the National Coalition for Health Professional Education in Genetics
and National Society of Genetic Counselors. This resource is for informa-
tional and educational purposes only.
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References
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Car:ick, J. A., Klola, E. M., Lambet-Messerlian, G. M., et a!. DNA
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ahead of print, May 14.
Devers, P., Cronister, A, Ormond, K., et al. Noninvasive Prenatal Testingl
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PortalsIO/AdvocacyINSGC%20Noninvaslve%20Prenatal%20Testing%20
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Norton ME, Brar H, Weiss J, et al. Non-Invasive Chromosomal
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Palomaki, G. E., Deciu, C., Klola, E. M" et al. DNA sequencing 01 mater-
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